Inertial Sensor Data Correction for Helmet-Mounted Displays
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Solution Overview
Problem
Existing helmet-mounted display systems face challenges in accurately determining orientation due to errors in inertial sensor data, particularly from miniature gyroscopes, which can result in bias errors, noise, and misalignment issues, leading to pilot nausea and inaccurate symbol positioning.
Innovation Solution
A method that combines inertial sensor data with non-inertial tracker system data to correct for errors by deriving rate data in inertial space, applying corrections for misalignment and bias, using a mapping between inertial sensor rate space and object orientation rate space, and employing filtering techniques to suppress noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If inertial sensors (miniature gyroscopes) are used to track orientation changes, then the system can provide rate data for orientation tracking, but errors due to bias, noise, and misalignment occur leading to inaccurate orientation determination
Solution Approach 1:
The patent combines data from inertial sensors (providing high-speed rate data) with data from a non-inertial tracker system (providing accurate absolute orientation references). By merging these two data sources and deriving rate data from the non-inertial system, the invention achieves both fast tracking response and high measurement accuracy, resolving the contradiction between speed and precision.
Solution Approach 2:
The system uses the non-inertial tracker system as a reference to generate correction data that feeds back to correct the inertial sensor measurements. This feedback mechanism allows the system to maintain the high-speed response of inertial sensors while continuously correcting their drift and errors, achieving both speed and accuracy.
2Measurement precision
If correction methods are applied to inertial sensor data using mapping between rate spaces, then accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary processing step that creates a mapping between inertial sensor rate space and object orientation rate space derived from non-inertial data. This mapping acts as a mediator that transforms the complex correction problem into a systematic coordinate transformation, improving accuracy while managing complexity through structured mathematical relationships.
Data Source
AI summary
A method is provided for determining corrections to rate data output by inertial sensors of a type typically used in tracking changes in orientation of an object. The present invention also extends to a tracker system incorporating the correction functionality of the present invention. The method makes use of rate data output by inertial sensors associated with the object being tracked and rate data derived from measures of orientation supplied by a non-inertial tracker system also associated with the object being tracked and comprises determining from those rate data corrections for errors due to misalignment in rate data output by inertial sensors, by calculating a mapping between vectors linking points in inertial sensor rate space represented by a sample set of received rate data from the inertial sensors and vectors linking points in a derived object orientation rate space represented by a corresponding and synchronised sample set of derived rate data. Corrections for inertial sensor bias may be determined separately from corrections for misalignment-related errors, after correction of inertial sensor rate data for misalignment-related errors by determining the vector translation between a point represented by corrected inertial sensor rate data in the derived object orientation rate space and the point in the same rate space represented by derived rate data synchronised therewith.